This invention relates generally to a time slot interchange network ("TSI network") and more particularly to a novel highly functional TSI network implemented with relatively few control components.
Telephone networks often multiplex numerous data channels onto a given data transmission medium. A "data channel" may represent an individual voice channel associated with a given telephone subscriber. A "data channel" may also represent a dedicated computer modem channel, a telephone network maintenance channel, or a previously multiplexed series of channels. "Data transmission medium" is not intended to be limited to any particular transmission medium, and includes, for example, wire transmission lines, radio frequency bandwidth, and lightwave transmission guides, such as fiber optic lines.
One known method of multiplexing channels of data is time division multiplexing.
Time division multiplexing assigns sequential time slots to a given data transmission medium. In this way, a given transmission medium may be divided into many discrete data channels. A composite signal of these time division multiplexed channels is referred to herein as a TDM signal.
TSI networks are typically used to manipulate data channels in a TDM signal. For example, a TSI network may be used to interchange channels between time slots within a given TDM signal. A TSI network may also be used to interchange channels between time slots in additional TDM signals. In this manner, transmission media may be groomed to achieve optimum capacity for a given TDM signal or route data channels to desired TDM signals.
Because a TSI network typically has access to individual data channels, it may become advantageous to perform signal processing in addition to merely re-sequencing data channels into different time slots. For example, it may be desirable to amplify or attenuate the signal level of a given voice channel. Additionally, it may be desirable to combine data channels. It may also be desirable to originate data channels with predetermined data.
This invention provides a novel and simple way to structure and implement a TSI network for a relatively large number of ports with minimal components. One embodiment of TSI network of the present invention allows the specification of time slot connections, amplification and attenuation values to apply to that connected data. In another embodiment, a constant pulse code modulation ("PCM") pattern to be delivered to an outgoing channel is specified. In another embodiment, all of the parameters are specified in a single microprocessor write cycle.
A time slot interchange is therefore provided having a time division multiplexed signal input port and time division multiplexed signal output port for interchanging time division multiplexed data channels. The time slot interchange comprises a data channel memory, coupled to the time division multiplexed signal input port, a channel circuit, having a write address output, the write address output connected to the data channel memory, a signal processing circuit, having a channel input coupled to the data channel memory, a gain input, and an output coupled to the time division multiplexed signal output port, and a connection memory, including a unique read channel field comprising a read address portion and a gain value portion for each data channel to be output by the time slot interchange network, the connection memory having an input connected to the write address output of the channel circuit, a read address output connected to the data channel memory, and a gain value output connected to the gain input of the signal processing circuit.